1. Field
This invention pertains to dehumidification and, in particular, to dehumidification by means of a cap containing a desiccant.
2. Prior Art
There are many and varied applications for desiccant caps intended to provide a low humidity atmosphere within an associated container. Material requiring such protection include pharmaceuticals, seeds, food and machinery. The need for a reliable, long lasting cap can be exemplified by the effect of moisture on special seeds, such as ornamental cactus seed. A relatively small bottle of these seeds may cost as much as $500. A short period of exposure to a moist atmosphere results in the sprouting and eventual destruction of the seeds. Damage is similarly incurred with many expensive pharmaceuticals when exposed to a humid atmosphere for a relatively short period of time.
An equally large number of desiccant caps have been designed to overcome these problems as indicated by U.S. Pat. Nos. 1,425,790, 1,637,656, 1,655,248, 2,317,882, 2,446,361, 2,487,620, 2,548,168 and 2,676,078. These devices usually include a perforated metal holder for a desiccant which is either held together by a binder, such as asbestos, or separated from the container contents by a fiberglass sheet. In some cases the fiberglass is eliminated and only the perforated shield is used to isolate the desiccant from the container contents.
Sealing of the container is usually accomplished by merely tightening the cap without a gasket. The results of these approaches has been inadequate. The dehumidification is short lived and the desiccant and carcenogenic materials, such as asbestos and fiberglass commingle with the container contents. The contents are often food or pharmaceuticals, making the use of such devices a serious health and product liability problem.
In a number of these prior art devices, an indication of the state of the desiccant cannot be determined by visual inspection or the cap must be removed to determine the desiccant state, which results in exposing the contents to moisture merely to perform an inspection.